<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
 <xs:element name="foo" type="C1" />
 <xs:complexType name="C1" >
    <xs:choice>
      <xs:element name="e1" type="C1" minOccurs="1" maxOccurs="3"/>
    </xs:choice>
 </xs:complexType>
</xs:schema>